Cordless or wireless telephones are typically home units that consist of a base unit and one or more remote units. An example of such a cordless telephone is seen in U.S. Pat. No. 4,989,230 to Gillig et al., assigned to Motorola, Inc., and is incorporated herein by reference. The remote units communicate with the base unit over radio frequencies (RF) typically within a range of 1000 feet of the base unit. The base unit is connected to the land-line telephone system, thus allowing a remote user to communicate with other land-line telephones.
The problem with this type of system, however, is that the RF signals can be received by anyone with a receiver tuned to the frequency being used by the cordless telephone. This makes it difficult to have a private conversation using a cordless telephone. Cordless telephones that scramble the RF voice signal don't provide for testing the scrambling function to determine if it is working properly. There is a resulting need for a cordless telephone that makes it difficult for the RF voice signals to be listened to and also enable the scrambling function to be checked for proper operation.